1. Field of the Invention
The present invention relates to a projector and a method of correcting the distortion of a projected image, and more particularly to a projector having a transmitter information receiver for utilizing information from a transmitter which has an ultrasonic transmission unit and an infrared emission unit, and a method of correcting the distortion of an image projected by such a projector.
2. Description of the Related Art
In recent years, efforts that have been made to shorten the focal length of projectors have resulted in a growing number of projectors available for projecting images over short distances. Greater focal length reductions have also been achieved by projectors having a projecting mirror disposed in a housing which has an open structure.
Images projected by short-focal-length projectors tend to suffer a very large distortion even if the screen is only slightly distorted or twisted. Such a very large distortion is caused because the distance between the projector and the screen is so small that the ratio of the screen distortion or twist to the distance is unduly large. Various difficulties have been experienced in manually adjusting installed projectors to correct image distortions.
JP-A-2003-324669 discloses a correcting process employing a mechanical tilt sensor mechanism for improving the adjustment of an installed projector. It has also been proposed to install a signal source for supplying positional information on a screen or to electrically detect the tilt of a projector itself to correct the tilt.
According to the correcting process disclosed in JP-A-2003-324669, the projector needs to have a space therein for mounting a tilt sensor therein. The disclosed process is unable to correct an image distortion due to the distortion or a twist of the screen itself. The signal source mounted on the screen for supplying positional information or the electrical detection of the tilt of the projector itself to correct the tilt has suffered a low accuracy of corrected images and can only be used with a limited range of projectors and screens.